CN114291825A - Process production line and process method for preparing caustic soda - Google Patents
Process production line and process method for preparing caustic soda Download PDFInfo
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- CN114291825A CN114291825A CN202111619240.6A CN202111619240A CN114291825A CN 114291825 A CN114291825 A CN 114291825A CN 202111619240 A CN202111619240 A CN 202111619240A CN 114291825 A CN114291825 A CN 114291825A
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Abstract
The invention provides a process production line and a process method for preparing caustic soda, wherein 32% of alkali liquor is used as a raw material and is put into a double-effect evaporator, and the alkali liquor is subjected to double-effect evaporation treatment and then enters a single-effect evaporator for single-effect evaporation; the alkali liquor discharged from the first-effect evaporator is divided, part of the alkali liquor is subjected to a finished product flake alkali procedure to obtain 50% finished product alkali, and part of the alkali liquor is configured into 61% alkali liquor by the pre-concentrator and enters a concentration system; feeding alkali liquor with the concentration of 61% into a membrane falling pipe for heating and concentrating, controlling the concentration of the alkali liquor to be 99%, feeding the concentrated alkali liquor into a finished product separator for separation, and distributing the separated alkali liquor to a plurality of caustic soda flake machines through an alkali liquor distributor for caustic soda flake preparation; and conveying the finished caustic soda flakes prepared by the caustic soda flake machine to a packaging station for packaging. The invention provides a complete caustic soda process production line, greatly improves the caustic soda preparation efficiency and effectively reduces energy loss.
Description
Technical Field
The invention relates to the technical field of caustic soda industrial equipment, in particular to a process production line and a process method for preparing caustic soda.
Background
Caustic soda is also known as caustic soda and caustic soda, and is a chemical name of sodium hydroxide, is a white solid at normal temperature, has strong corrosivity, is easily dissolved in water, and is a very common alkali, and an aqueous solution of the caustic soda is strong alkaline. Commercially available caustic soda is available in both solid and liquid states: the solid is white, and has the characteristics of block, sheet, rod, particle and crisp texture; the pure liquid caustic soda is colorless transparent liquid. The caustic soda is widely applied to various industries such as chemical industry, printing and dyeing, papermaking, environmental protection and the like, and is divided into an industrial grade and a food grade (a food additive, namely sodium hydroxide), the two industries are mainly different in purity, but have different contents of toxic substances such as lead, arsenic, mercury and the like, and the industrial grade cannot be applied to the food industry due to higher content of the toxic substances.
In the production line of the caustic soda preparation process, the energy consumption is too large, so that the improvement of the existing process production line is necessary.
Disclosure of Invention
The invention aims to solve the technical problem of overcoming the defects in the prior art and provides a process production line and a process method for preparing caustic soda.
In order to solve the technical problems, the invention adopts the following technical scheme:
according to the first technical scheme, the invention provides a process production line for preparing caustic soda, wherein an evaporation unit comprises a first-effect evaporator, a second-effect evaporator, an alkali water heat exchanger, an alkali liquid cooler and an air-blocking drainage tank;
the secondary steam outlet end of the first-effect evaporator is connected with the steam inlet end of the second-effect evaporator through a first evaporation pipeline, the condensed water outlet end of the first-effect evaporator is connected with the inlet end of the air-blocking water drainage tank through a second evaporation pipeline, and the outlet end of the air-blocking water drainage tank is connected with the water inlet end of the alkali water heat exchanger through a third evaporation pipeline; the feed end of the second-effect evaporator is used for feeding raw material alkali liquor, the discharge end of the second-effect evaporator is respectively connected with the first alkali liquor inlet end of the alkali-alkali heat exchanger and the liquid inlet end of the alkali-alkali heat exchanger through a fourth evaporation pipeline, the first alkali liquor outlet end of the alkali-alkali heat exchanger and the liquid outlet end of the alkali-alkali heat exchanger are respectively connected with a sixth evaporation pipeline, the fourth evaporation pipeline is provided with a second alkali pump, the sixth evaporation pipeline is connected with the feed end of the first-effect evaporator, the discharge end of the first-effect evaporator is connected with the eighth evaporation pipeline and the ninth evaporation pipeline through a seventh evaporation pipeline, a first alkali pump is arranged on the seventh evaporation pipeline, valves are arranged on the eighth evaporation pipeline and the ninth evaporation pipeline, the eighth evaporation pipeline is connected with a second alkali liquor inlet end of the alkali liquor heat exchanger, and a second alkali liquor outlet end of the alkali liquor heat exchanger is connected with an alkali liquor inlet end of the alkali liquor cooler; the ninth evaporation pipeline is connected with the feed end of the concentration unit, and a preconcentrator is arranged on the ninth evaporation pipeline;
the concentration unit comprises a membrane falling pipe, a finished product separator, an alkali liquor distributor, a flake alkali machine, a molten salt device and an air preheater, wherein a feed end, a discharge end, a molten salt inlet end and a molten salt outlet end are respectively arranged on the membrane falling pipe; the molten salt device comprises a molten salt tank, a molten salt pump, a molten salt furnace and a burner, wherein at least one molten salt inlet end is arranged on the molten salt tank, the molten salt pump is arranged on the molten salt tank, one end of the molten salt pump extends into the molten salt tank through a first connecting pipe, the other end of the molten salt pump is connected with the liquid inlet end of the molten salt furnace through a second connecting pipe, the liquid outlet end of the molten salt furnace is connected with a third connecting pipe, the third connecting pipe is connected with the molten salt inlet end of the molten salt tank through a first pipeline, the third connecting pipe is connected with the molten salt inlet end of the falling film pipe through a second pipeline, the molten salt outlet end of the falling film pipe is connected with the molten salt tank through a return pipe, valves are arranged on the first pipeline and the second pipeline, the burner is arranged on the molten salt furnace and is used for providing heating energy for the molten salt furnace through the burner, a smoke outlet end is arranged on the molten salt furnace; the air inlet end of the air preheater is connected with the dust removal fan, and the air outlet end of the air preheater is connected with the air inlet of the combustor through a fourth connecting pipe.
As the preferred technical scheme, still include circulating water pipeline, circulating water pipeline includes circulation inlet tube and circulation outlet pipe, the water tank is connected to the one end of circulation inlet tube, and its other end is connected the flake alkali machine, the one end of circulation outlet pipe is connected the flake alkali machine, and its other end is connected the water tank.
As a preferred technical scheme, a conveying device is arranged corresponding to a finished product caustic soda discharge end of the caustic soda flake machine.
As a preferred technical scheme, the evaporation unit further comprises a condenser and a condensate tank, wherein a secondary steam outlet end of the secondary evaporator is connected with an inlet end of the condenser through a first water pipe, an outlet end of the condenser is connected with the condensate tank through a second water pipe, and a condensate outlet end of the secondary evaporator is connected with the condensate tank.
As a preferred technical scheme, a non-condensable gas outlet end of the condenser is connected with an evacuation pipe, and a vacuum pump is installed on the evacuation pipe.
As a preferable technical solution, the condensate tank is connected to a fifth evaporation pipeline, and a condensate pump is arranged on the fifth evaporation pipeline.
According to a preferable technical scheme, a cooling water inlet end of the condenser is connected with a first circulating water feeding pipe, and a cooling water outlet end of the condenser is connected with a first circulating water return pipe.
As a preferable technical scheme, a cooling water inlet end of the alkali liquor cooler is connected with a first circulating water feeding pipe, and a cooling water outlet end of the alkali liquor cooler is connected with a first circulating water return pipe.
As a preferred technical scheme, the alkali liquor outlet end of the alkali liquor cooler is connected with the flake caustic machine through an evaporation pipeline.
As a preferable technical scheme, the steam inlet end of the one-effect evaporator is connected with a steam pipe for introducing hot steam with the pressure of 0.6-0.8 Mpa.
According to a second technical solution of the present invention, there is provided a process for preparing caustic soda, which is characterized in that based on the above process line, the process comprises the following steps:
putting 32% alkali liquor as a raw material into a two-effect evaporator, and performing two-effect evaporation treatment, and then entering the first-effect evaporator for one-effect evaporation;
the alkali liquor discharged from the first-effect evaporator is divided, part of the alkali liquor is subjected to a finished product flake alkali procedure to obtain 50% finished product alkali, and part of the alkali liquor is prepared into 61% alkali liquor with concentration and enters a concentration system;
feeding alkali liquor with the concentration of 61% into a membrane falling pipe for heating and concentrating, controlling the concentration of the alkali liquor to be 99%, feeding the concentrated alkali liquor into a finished product separator for separation, and distributing the separated alkali liquor to a plurality of caustic soda flake machines through an alkali liquor distributor for caustic soda flake preparation;
and conveying the finished caustic soda flakes prepared by the caustic soda flake machine to a packaging station for packaging.
Compared with the prior art, the invention has the beneficial effects that:
32% NaOH (75 ℃, 0.4MPa) solution from the outside of the battery limits is added into a double-effect evaporator, and the concentration is increased from 32% to 39% (83 ℃, 85 KPa). After being concentrated, the alkali liquor is pressurized by a double-effect alkali pump, heated by a condensate water heat exchanger and an alkali heat exchanger and then enters an I-effect falling-film evaporator, and the concentration is increased to 50% (145 ℃, 10 kpa). The alkali liquor reaching the concentration is pressurized by a single-effect alkali pump, then is sent to a concentration flaking unit or outside a battery compartment after being subjected to heat recovery by an alkali exchanger and an alkali liquor cooler. The 50% NaOH (75 ℃, 0.4MPa) solution from the evaporation unit was added to the preconcentrator, increasing the concentration from 50% to 61% (105 ℃, 85 KPa). After being concentrated, the alkali liquor is pressurized by a 61% alkali pump, enters a final concentrator, is increased to 98% concentration by a flash tank (400 ℃, normal pressure), molten alkali enters a flake alkali machine by gravity to be cooled and sliced, and the flake alkali enters two full-automatic packaging machines and is packaged into 25 kg per bag. Therefore, a complete caustic soda process production line is formed, the caustic soda preparation efficiency is greatly improved, the steam consumption is reduced, and the purpose of energy conservation is achieved.
Drawings
In order to more clearly illustrate the detailed description of the invention or the technical solutions in the prior art, the drawings that are needed in the detailed description of the invention or the prior art will be briefly described below. Throughout the drawings, like elements or portions are generally identified by like reference numerals. In the drawings, elements or portions are not necessarily drawn to scale.
FIG. 1 is a schematic diagram of an evaporation unit of a flake caustic soda preparation system according to an embodiment of the present invention.
FIG. 2 is a schematic diagram of a concentration unit of a flake caustic soda preparation system according to an embodiment of the present invention.
In the figure, 101 is a first-effect evaporator, 102 is a second-effect evaporator, 103 is an alkali-water heat exchanger, 104 is an alkali-water heat exchanger, 105 is an alkali-water cooler, 106 is a choke drain tank, 107 is a first evaporation pipe, 108 is a second evaporation pipe, 109 is a third evaporation pipe, 110 is a fourth evaporation pipe, 111 is a sixth evaporation pipe, 112 is a second alkali pump, 113 is a seventh evaporation pipe, 114 is an eighth evaporation pipe, 115 is a ninth evaporation pipe, 116 is a first alkali pump, 117 is a valve, 118 is a condenser, 119 is a condensate tank, 120 is a first water pipe, 121 is a second water pipe, 122 is an evacuation pipe, 123 is a fifth evaporation pipe, 124 is a condensate pump, 125 is a first circulation water supply pipe, 126 is a first circulation water return pipe, 127 is a second circulation water supply pipe, 128 is a second circulation water return pipe, 129 is a vacuum pump, 130 is a vacuum pump, and 131 is a preconcentrator; 200 is a concentration system, 201 is a falling film tube, 202 is a finished product separator, 203 is an alkali liquor distributor, 204 is a caustic soda flake machine, 205 is a feed end, 206 is a discharge end, 207 is a molten salt inlet end, 208 is a molten salt outlet end, 209 is a circulating water inlet tube, 210 is a circulating water outlet tube, 211 is a molten salt tank, 212 is a molten salt pump, 213 is a molten salt furnace, 214 is a burner, 215 is a molten salt inlet end, 216 is a first connecting tube, 217 is a second connecting tube, 218 is a third connecting tube, 219 is a first pipeline, 220 is a second pipeline, 221 is a valve, 222 is a flue gas outlet end, 223 is an air preheater, 224 is a dust removal fan, 225 is a fourth connecting tube, 226 is a fifth connecting tube, 227 is a chimney, 228 is a sixth connecting tube, 229 is a seventh connecting tube, 230 is a first pressure gauge, 231 is a first temperature gauge, 232 is a third temperature gauge, 233 is a second pressure gauge, 234 is a second temperature gauge, and 235 is a conveying device.
Detailed Description
The technical solutions in the embodiments of the present invention will be described clearly and completely below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that all the directional indicators (such as upper, lower, left, right, front and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the movement situation, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.
In addition, the descriptions related to "first", "second", etc. in the present invention are only for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
The invention will now be further described with reference to the accompanying drawings.
The embodiment of the invention provides a process production line for preparing caustic soda. The production line comprises an evaporation unit and a concentration unit. And treating the alkali liquor by an evaporation unit and a concentration unit in sequence to obtain the finished product flake alkali.
Fig. 1 shows a schematic diagram of an evaporation unit structure of a process line for preparing caustic soda according to an embodiment of the present invention. As shown in FIG. 1, the evaporation unit comprises a single-effect evaporator 101, a double-effect evaporator 102, an alkali water heat exchanger 103, an alkali-alkali heat exchanger 104, an alkali liquor cooler 105 and a gas-tight drainage tank 106.
The secondary steam outlet end of the first-effect evaporator 101 is connected with the steam inlet end of the second-effect evaporator 102 through a first evaporation pipeline 107, the condensed water outlet end of the first-effect evaporator 101 is connected with the inlet end of the air-blocking water drainage tank 106 through a second evaporation pipeline 108, and the outlet end of the air-blocking water drainage tank 106 is connected with the water inlet end of the alkali water heat exchanger 103 through a third evaporation pipeline 109; the feed end of the second-effect evaporator 102 is used for feeding raw material alkali liquor, the discharge end of the second-effect evaporator 102 is connected with the first alkali liquor inlet end of the alkali-alkali heat exchanger 104 and the liquid inlet end of the alkali-alkali heat exchanger 103 through a fourth evaporation pipeline 110, the first alkali liquor outlet end of the alkali-alkali heat exchanger 104 and the liquid outlet end of the alkali-alkali heat exchanger 103 are connected with a sixth evaporation pipeline 111 respectively, a second alkali pump 112 is arranged on the fourth evaporation pipeline 110, the sixth evaporation pipeline 111 is connected with the feed end of the first-effect evaporator 101, the discharge end of the first-effect evaporator 101 is connected with an eighth evaporation pipeline 114 and a ninth evaporation pipeline 115 through a seventh evaporation pipeline 113, a first alkali pump 116 is arranged on the seventh evaporation pipeline 113, valves 117 are arranged on the eighth evaporation pipeline 114 and the ninth evaporation pipeline 115, and the eighth evaporation pipeline 114 is connected with the second alkali liquor inlet end of the alkali-alkali heat exchanger 104, the second alkali liquor outlet end of the alkali liquor heat exchanger 104 is connected with the alkali liquor inlet end of the alkali liquor cooler 105.
The process production line and the process method for preparing the caustic soda provided by the embodiment of the invention utilize a counter-current multi-effect evaporation principle. As shown in FIG. 1, the arrows in FIG. 1 indicate the direction of the steam, the condensed water and the lye. In general, the alkali liquor flows from the second-effect evaporator 102 to the first-effect evaporator 101 and then flows out from the first-effect evaporator 101 to the finished alkali liquor or the next process flow, the direction of the steam is opposite, the steam flows from the first-effect evaporator 101 to the second-effect evaporator 102, and the secondary steam from the second-effect evaporator 102 is not used again because the energy which can be used by the secondary steam is very low.
In the process that the alkali liquor flows to the first-effect evaporator 101 from the second-effect evaporator 102, the temperature needs to be adjusted first and then the alkali liquor enters the first-effect evaporator 101, and an alkali-alkali heat exchanger 104 and an alkali-alkali heat exchanger 103 are arranged to adjust the temperature in the embodiment of the invention.
The principle of selecting the alkali-alkali heat exchanger 104 for heat exchange is as follows: the lye originally coming out of the one-effect evaporator 101 through the seventh evaporation pipe 113 and the eighth evaporation pipe 114 is utilized, and the part of lye is fed into the preparation process of the next finished product process through the lye cooler 15. Because the part of the alkali liquor just needs to be cooled, the part of the alkali liquor can be used as a heat exchange medium to exchange heat with the alkali liquor discharged from the double-effect evaporator 12, so that the utilization rate of heat can be improved.
The principle of heat exchange by selecting the alkaline water heat exchanger 103 is as follows: the condensed water outlet end of the first-effect evaporator 101 is connected with the inlet end of the air-blocking water drainage tank 106 through a second evaporation pipeline 108, and the outlet end of the air-blocking water drainage tank 106 is connected with the water inlet end of the alkali water heat exchanger 103 through a third evaporation pipeline 109, so that the condensed water from the first-effect evaporator 101 and the alkali water from the second-effect evaporator 102 exchange heat.
The alkali liquor discharged from the alkali-alkali heat exchanger 104 and the alkali-alkali heat exchanger 103 is mixed in the sixth evaporation pipeline 111 to realize the temperature adjustment of the alkali liquor, and the alkali liquor with the adjusted temperature enters the first-effect evaporator 101 through the feed end of the first-effect evaporator 101 to be evaporated.
In the embodiment of the present invention, as shown in fig. 1, the evaporation unit further includes a condenser 118 and a condensate tank 119, the secondary steam outlet end of the second-effect evaporator 105 is connected to the inlet end of the condenser 118 through a first water pipe 120, the outlet end of the condenser 118 is connected to the condensate tank 119 through a second water pipe 121, and the condensate outlet end of the second-effect evaporator 102 is connected to the condensate tank 119.
In the embodiment of the present invention, in consideration of the discharge of the non-condensable gas of the condensed water, as shown in fig. 1, the non-condensable gas outlet end of the condenser 118 is connected to an evacuation pipe 122, and a vacuum pump 130 is installed on the evacuation pipe 122. The non-condensable gasses from the condenser 118 are exhausted through the exhaust pipe 122 by the air pump 130.
In the embodiment of the present invention, the condensate tank 119 is connected to a fifth evaporation pipe 123, and a condensate pump 124 is disposed on the fifth evaporation pipe 123. When the condensate collected in the condensate tank 119 is full, the condensate is drained to a condensate temporary storage device through the fifth evaporation pipeline 123 for storage, and the condensate temporary storage device can be a liquid tank or a large-volume liquid tank and the like.
In the embodiment of the present invention, the heat exchange medium of the condenser 118 is preferably cooling water, so that a first circulating water feeding pipe 125 may be connected to a cooling water inlet end of the condenser 118, and a first circulating water returning pipe 126 may be connected to a cooling water outlet end of the condenser 118. The first circulating water supply pipe 125 may be connected to a water tank storing cooling water to provide cooling water, and the first circulating water return pipe 126 is connected to a storage device for recovering the cooling water after heat exchange. The temperature of the cooling water is determined according to an actual process, and may be, for example, 8 °, 10 °, 15 °, and the like, and embodiments of the present invention are not particularly limited thereto.
In the embodiment of the present invention, the heat exchange medium of the lye cooler 105 is preferably water, the cooling water inlet end of the lye cooler 105 is connected to the second circulating water supply pipe 127, and the cooling water outlet end of the lye cooler is connected to the second circulating water return pipe 128. The cooling water outlet end of the alkali liquor cooler 105 is connected with a first circulating water return pipe 126. The second circulation water supply pipe 127 may be connected to a water tank storing cooling water to provide cooling water, and the second circulation water return pipe 128 is connected to a storage device for recovering the cooling water after heat exchange. The temperature of the cooling water is determined according to an actual process, and may be, for example, 8 °, 10 °, 15 °, and the like, and embodiments of the present invention are not particularly limited thereto.
In the embodiment of the invention, the alkali liquor outlet end of the alkali liquor cooler 105 is connected with the flake caustic machine through an evaporation pipeline.
In the embodiment of the invention, the steam inlet end of the single-effect evaporator is connected with a steam pipe 129 for introducing hot steam with the pressure of 0.6-0.8 Mpa.
The concentration of the alkali liquor discharged after the treatment of the evaporation unit 100 provided in the embodiment of the present invention is 50%, and the concentration is increased to 61% by the pre-concentrator 131, and then the alkali liquor is used as the raw material of the concentration unit. The following embodiments of the present invention will further illustrate the specific functional principle of the present invention by combining with the specific structure of the concentration unit.
Fig. 2 shows a schematic diagram of a concentration unit structure of a process line for preparing caustic soda according to an embodiment of the present invention. As shown in fig. 2, the concentration unit 200 includes a membrane lowering pipe 201, a finished product separator 202, a lye distributor 203, and a caustic soda flake machine 204, wherein the membrane lowering pipe 201 is provided with a feed end 205, a discharge end 206, a molten salt inlet end 207, and a molten salt outlet end 208, the discharge end 206 provided on the membrane lowering pipe 201 is connected to the finished product separator 202 through a pipeline, the finished product separator 202 is connected to the lye distributor 203 through a pipeline, the lye distributor 203 is connected to the caustic soda flake machine 204 through a pipeline, the caustic soda flake machine is provided in plurality, and one lye distributor is connected to a plurality of caustic soda flake machines 204 through a plurality of pipelines. In the embodiment, two caustic soda flakers 204 are illustrated, and may be provided in a plurality of numbers, such as 3, 4, 5, etc., according to actual needs. The embodiment of the present invention is not particularly limited thereto.
In practice, 61% strength lye from the evaporation unit 100 is fed through the feed end 205 of the downcomer 201. The heat of the falling film tube 201 comes from high-temperature molten salt, and the high-temperature molten salt enters the falling film tube 201 from the molten salt inlet end 207 to heat and concentrate the alkali liquor and then flows out from the molten salt outlet end 208. The concentrated alkali liquor enters a finished product separator 202, the finished product separator is actually a vapor-liquid separator, secondary vapor is sent to an evaporation unit through a vapor outlet of the finished product separator 202 to avoid alkali liquor loss, the alkali liquor enters a liquid inlet distributor 203 to be distributed to a plurality of flake caustic soda machines for flake caustic soda preparation, and the prepared flake caustic soda can be conveyed into the next station (such as packaging and the like) through a conveying device 235 (such as a conveying belt) arranged corresponding to a finished product flake caustic soda discharge end of the flake caustic soda machine 204. Therefore, the concentration system in the embodiment of the invention can complete the concentration of the high-concentration alkali liquor and can be matched with the preparation of finished caustic soda flakes, so that the concentration system is a perfect concentration system, and particularly in the caustic soda preparation process, the concentration efficiency of the alkali liquor and the preparation efficiency of the caustic soda flakes are greatly improved.
In one embodiment, the system further comprises a circulating water pipeline, the circulating water pipeline comprises a circulating water inlet pipe 209 and a circulating water outlet pipe 210, one end of the circulating water inlet pipe 209 is connected with a water tank (not shown in the figure), the other end of the circulating water inlet pipe 209 is connected with the flake caustic machine 204, and one end of the circulating water outlet pipe 209 is connected with the flake caustic machine 204, and the other end of the circulating water outlet pipe 209 is connected with the water tank.
In the embodiment of the present invention, the concentration unit further includes a molten salt device, wherein the molten salt device includes a molten salt tank 211, a molten salt pump 212, a molten salt furnace 213, and a burner 214, at least one molten salt inlet end 215 is disposed on the molten salt tank 211, the molten salt pump 212 is mounted on the molten salt tank 211, one end of the molten salt pump 212 extends into the molten salt tank 211 through a first connection pipe 216, the other end of the molten salt pump 212 is connected to the liquid inlet end of the molten salt furnace 213 through a second connection pipe 217, the liquid outlet end of the molten salt furnace 213 is connected to a third connection pipe 218, the third connection pipe 218 is connected to the molten salt inlet end 215 of the molten salt tank 211 through a first pipeline 219, and the third connection pipe 218 is connected to the liquid inlet end 205 through a second pipeline 210, and is configured to convey the heated molten salt into the falling film pipe 201 to heat the concentrated alkali liquor, valves 221 are disposed on the first pipeline 219 and the second pipeline 220, the burner 214 is arranged on the molten salt furnace 213 and is used for providing heating energy for the molten salt furnace 213 through the burner 214, and the flue gas outlet end 222 is arranged on the molten salt furnace 213. The molten salt tank 211 is used for holding low-temperature molten salt, when the molten salt tank is in operation, the molten salt in the molten salt tank 211 is input into the molten salt furnace 213 through the molten salt pump 213, and the burner 214 provides energy for heating the molten salt for the molten salt furnace 213. The burner 214 may be a gas burner or an oil burner or a coal burner depending on the kind of fuel. After the low-temperature molten salt is heated in the molten salt furnace 213, the low-temperature molten salt is respectively connected with a first pipeline 219 and a second pipeline 220 through a third connecting pipe 218, wherein a second pressure gauge 233 and a second thermometer 234 are arranged on the third connecting pipe 218 and are used for monitoring the temperature of the high-temperature molten salt coming out of the molten salt furnace 213, when the temperature of the molten salt is judged to reach the designed temperature, a valve on the first pipeline is opened and is used for taking the high-temperature molten salt as a heat source for heating concentrated alkali liquor by a final concentrator, and the low-temperature molten salt after heat exchange is recycled into a molten salt tank 211 and is conveyed into the molten salt furnace through a molten salt pump again for cyclic heating; if the temperature does not reach the design temperature, a valve on the second pipeline is opened, the molten salt is recycled into the molten salt groove 211, and the molten salt is conveyed to the molten salt furnace through the molten salt pump again for cyclic heating. Thus, a system using high-temperature molten salt is required to complete the matching.
In addition, regarding the heating part, the design of an air preheater 223 may be added, wherein the air inlet end of the air preheater 223 is connected with a dust removal fan 224, and the air outlet end of the air preheater 223 is connected with the air inlet of the burner 214 through a fourth connecting pipe 225. The air preheater 213 is used to raise the temperature of the air entering the burner, and the dust removal fan 224 is used to remove the particles contained in the air, so as to prevent the dust contained in the air from entering the burner 214 to affect the combustion or affect the service life of the components inside the burner 214. The preheated air can ensure the success rate of ignition of the burner 214 and can prevent air with too low temperature from entering the burner 214 to affect the combustion operation of the burner 214.
When the temperature of the tail gas generated in the system is not high, the flue gas outlet end 222 is connected with a chimney 227 through a fifth connecting pipe 226, and the tail gas is directly discharged. If a large amount of harmful substances in the air are generated as fuel, the exhaust gas should be treated and then discharged.
Further, referring to fig. 2, the flue gas outlet port 2222 is connected to the air preheater 223 through a sixth connection pipe 228, and an air outlet of the air preheater 223 is connected to the chimney 227 through a seventh connection pipe 229. Considering the existence of waste heat in the tail gas, the flue gas generated by combustion can preheat combustion air through an air preheater to recover heat.
When the coal is used as fuel, because the temperature of the flue gas is high, the heat in the flue gas can be recycled again by adding a waste heat boiler, and the utilization rate of high energy is improved.
In one embodiment, referring to fig. 2, a first pressure gauge 230 and a first temperature gauge 231 are disposed on the molten salt furnace 213 for monitoring temperature and pressure values in the molten salt furnace 213. The molten salt tank 211 is provided with a third thermometer 232 for monitoring the temperature value of the molten salt in the molten salt tank 211.
The embodiment of the invention provides a process method for preparing caustic soda, which is based on the process production line provided by the various embodiments of the invention. The method mainly comprises double-effect falling film evaporation and pre-concentration and final concentration:
the double-effect evaporation process comprises the following steps: 32% NaOH (75 ℃, 0.4MPa) solution sent from the outside of the battery limits is added into the II-effect falling-film evaporator, and the concentration is increased from 32% to 39% (83 ℃, 85 KPa). After being concentrated, the alkali liquor is pressurized by a II-effect alkali pump, heated by a condensate water heat exchanger and an alkali heat exchanger and then enters an I-effect falling-film evaporator, and the concentration is increased to 50 percent (145 ℃, 10 kpa). The alkali liquor reaching the concentration is pressurized by an I-effect alkali pump, then is subjected to heat recovery by an alkali exchanger and an alkali liquor cooler, and is simultaneously conveyed to a concentration flaking unit or outside a battery compartment.
Raw steam of 0.8MPaG passes through a steam regulating valve and then enters a heating chamber of the I-effect evaporator, and steam condensate water is subjected to heat exchange by a condensate water converter to recover heat and then is sent out of a boundary area by self pressure for use. The secondary steam generated by the I-effect evaporation is used as a heating medium of the II-effect evaporator, and the II-effect condensate water enters the condensate water tank. The secondary steam generated by the II-effect evaporation is condensed in the surface condenser, the vacuum pump sucks negative pressure, and the generated condensate enters the condensate water tank and is uniformly pumped out of the boundary area by the condensate water pump for use.
The pre-concentration and final concentration process is as follows:
the 50% NaOH (75 ℃, 0.4MPa) solution from the evaporation unit of the apparatus was added to the preconcentrator, increasing the concentration from 50% to 61% (105 ℃, 85 KPa). After being concentrated, the alkali liquor is pressurized by a 61% alkali pump, enters a final concentrator, is increased to 98% concentration by a flash tank (400 ℃, normal pressure), molten alkali enters a flake alkali machine by gravity to be cooled and sliced, and the flake alkali enters two full-automatic packaging machines and is packaged into 25 kg per bag. The packing machine is provided with an air exhaust facility, and dust is pumped into the washing tank for dust removal.
The secondary steam generated by the preconcentrator is condensed in the surface condenser, the vacuum pump pumps negative pressure, and the generated condensate enters a concentrated condensate water tank. Condensate generated by preconcentration enters a concentrated condensate water tank after passing through a steam-blocking and water-draining tank, then condensate water is used by itself through a condensate water pump, and the residual condensate water is output to a boundary area.
The heat required for the concentration of the lye from 50% to 61% is supplied by the secondary steam of the final concentrator. The heat required to condense the lye from 61% to 98% is provided by the molten salt which is forced by a molten salt pump through a natural gas-fueled molten salt furnace, the temperature of which is raised to about 425 ℃. And the flue gas generated by the molten salt furnace is used as combustion-supporting air of the molten salt furnace burner after cold air sent by the blower is preheated by the air preheater.
The above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; such modifications and substitutions do not depart from the spirit and scope of the present invention, and they should be construed as being included in the following claims and description.
Claims (10)
1. A process production line for preparing caustic soda is characterized by comprising an evaporation unit and a concentration unit,
the evaporation unit comprises a first-effect evaporator, a second-effect evaporator, an alkali water heat exchanger, an alkali liquid cooler and an air-blocking drainage tank;
the secondary steam outlet end of the first-effect evaporator is connected with the steam inlet end of the second-effect evaporator through a first evaporation pipeline, the condensed water outlet end of the first-effect evaporator is connected with the inlet end of the air-blocking water drainage tank through a second evaporation pipeline, and the outlet end of the air-blocking water drainage tank is connected with the water inlet end of the alkali water heat exchanger through a third evaporation pipeline; the feed end of the second-effect evaporator is used for feeding raw material alkali liquor, the discharge end of the second-effect evaporator is respectively connected with the first alkali liquor inlet end of the alkali-alkali heat exchanger and the liquid inlet end of the alkali-alkali heat exchanger through a fourth evaporation pipeline, the first alkali liquor outlet end of the alkali-alkali heat exchanger and the liquid outlet end of the alkali-alkali heat exchanger are respectively connected with a sixth evaporation pipeline, the fourth evaporation pipeline is provided with a second alkali pump, the sixth evaporation pipeline is connected with the feed end of the first-effect evaporator, the discharge end of the first-effect evaporator is connected with the eighth evaporation pipeline and the ninth evaporation pipeline through a seventh evaporation pipeline, a first alkali pump is arranged on the seventh evaporation pipeline, valves are arranged on the eighth evaporation pipeline and the ninth evaporation pipeline, the eighth evaporation pipeline is connected with a second alkali liquor inlet end of the alkali liquor heat exchanger, and a second alkali liquor outlet end of the alkali liquor heat exchanger is connected with an alkali liquor inlet end of the alkali liquor cooler;
the ninth evaporation pipeline is connected with the feed end of the concentration unit, and a preconcentrator is arranged on the ninth evaporation pipeline;
the concentration unit comprises a membrane falling pipe, a finished product separator, an alkali liquor distributor, a flake alkali machine, a molten salt device and an air preheater, wherein a feed end, a discharge end, a molten salt inlet end and a molten salt outlet end are respectively arranged on the membrane falling pipe; the molten salt device comprises a molten salt tank, a molten salt pump, a molten salt furnace and a burner, wherein at least one molten salt inlet end is arranged on the molten salt tank, the molten salt pump is arranged on the molten salt tank, one end of the molten salt pump extends into the molten salt tank through a first connecting pipe, the other end of the molten salt pump is connected with the liquid inlet end of the molten salt furnace through a second connecting pipe, the liquid outlet end of the molten salt furnace is connected with a third connecting pipe, the third connecting pipe is connected with the molten salt inlet end of the molten salt tank through a first pipeline, the third connecting pipe is connected with the molten salt inlet end of the falling film pipe through a second pipeline, the molten salt outlet end of the falling film pipe is connected with the molten salt tank through a return pipe, valves are arranged on the first pipeline and the second pipeline, the burner is arranged on the molten salt furnace and is used for providing heating energy for the molten salt furnace through the burner, a smoke outlet end is arranged on the molten salt furnace; the air inlet end of the air preheater is connected with the dust removal fan, and the air outlet end of the air preheater is connected with the air inlet of the combustor through a fourth connecting pipe.
2. The process production line of claim 1, further comprising a circulating water pipeline, wherein the circulating water pipeline comprises a circulating water inlet pipe and a circulating water outlet pipe, one end of the circulating water inlet pipe is connected with the water tank, the other end of the circulating water inlet pipe is connected with the flake caustic soda machine, one end of the circulating water outlet pipe is connected with the flake caustic soda machine, and the other end of the circulating water outlet pipe is connected with the water tank.
3. A process line according to claim 1, wherein a conveying means is provided in correspondence of the finished caustic soda flake discharge end of the caustic soda flake machine.
4. The process production line of claim 1, wherein the evaporation unit further comprises a condenser and a condensate tank, wherein a secondary steam outlet end of the secondary evaporator is connected with an inlet end of the condenser through a first water pipe, an outlet end of the condenser is connected with the condensate tank through a second water pipe, and a condensate outlet end of the secondary evaporator is connected with the condensate tank.
5. The process production line of claim 4, wherein the non-condensable gas outlet end of the condenser is connected with an evacuation pipe, and a vacuum pump is mounted on the evacuation pipe.
6. The process line according to claim 4, wherein the condensate tank is connected to a fifth evaporation pipe, and a condensate pump is arranged on the fifth evaporation pipe.
7. The process production line of claim 4, wherein the cooling water inlet end of the condenser is connected with a first circulating water feeding pipe, and the cooling water outlet end of the condenser is connected with a first circulating water returning pipe.
8. The process production line of claim 1, wherein the cooling water inlet end of the lye cooler is connected with the first circulating water supply pipe, and the cooling water outlet end of the lye cooler is connected with the first circulating water return pipe.
9. The process line of claim 1, wherein the lye outlet end of the lye cooler is connected to the flake caustic machine by an evaporation pipe.
10. A process for the preparation of caustic soda, based on the process line according to any one of claims 1 to 9, comprising the following steps:
putting 32% alkali liquor as a raw material into a two-effect evaporator, and performing two-effect evaporation treatment, and then entering the first-effect evaporator for one-effect evaporation;
the alkali liquor discharged from the first-effect evaporator is divided, part of the alkali liquor is subjected to a finished product flake alkali procedure to obtain 50% finished product alkali, and part of the alkali liquor is configured into 61% alkali liquor by the pre-concentrator and enters a concentration system;
feeding alkali liquor with the concentration of 61% into a membrane falling pipe for heating and concentrating, controlling the concentration of the alkali liquor to be 99%, feeding the concentrated alkali liquor into a finished product separator for separation, and distributing the separated alkali liquor to a plurality of caustic soda flake machines through an alkali liquor distributor for caustic soda flake preparation;
and conveying the finished caustic soda flakes prepared by the caustic soda flake machine to a packaging station for packaging.
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